Recently, with development of a computer technique that is applied to the medical field, the diagnosis of a human body and structural analysis are commonly performed based on 3-dimensional data obtained by CT and MRI. Additionally, in the field of dentistry, a 3-dimensional imaging technique is used for a study to form a 3-dimensional model of the temporomandibular joint from data filmed by CT, for example, Yoshinori Arai, Koji Hashimoto, Hiroshi Shinoda, “Development in 3D imaging program for small field-sized X-ray computed tomography (an Ortho-CT image) for dentistry use”, Dentistry Radioactive Rays, 39 “4” P224–P229, 2000.
However, there still remain lots of things in which the operator is involved to process the CT image in the conventional study. Therefore, it is desired that a system can semi-automatically create, based on the data obtained by CT, a 3-dimensional model that the operator can process afterward.
Additionally, a CT image of the temporomandibular joint requires a plurality of transmitted images or reflective images taken by applying radiation to a body. The amount of radiation applied to the body must be minimized so as to not expose the body to excessive radiation.
However, the CT image obtained by weak radiation is noisy. In the case of a CT apparatus for the temporomandibular joint, the amount of X-ray radiation is limited to about 1/100 of that of a conventional CT apparatus for general medical use. The 3-dimensional image obtained by such a weak X-ray radiation sometimes is partially not clear enough for dental use.